Wednesday, 12 November 2014

I was surprised to find a design from Pieter, PE1ODJ, in my mailbox. It shows a simple design for a proposed baseband circuit.The circuit combines 2 audio carrier waves (at 7.02 and 7.2 MHz) with a video signal.The audio carrier waves are combined in a one transistor common base circuit with an amplification factor 2. Due to the low resistance input at the emitter intermodulation between the 7 MHz audio signals is prevented.The video signal is fed through a transformer-bridge circuit. The transformer uses a T50-2 Amidon core. This circuit garantees a good seperation between video and audio signals.November 23 this circuit was succesfully activated in combination with my 13 cm ATV QRP transmitter (with one 7 MHz oscillator). Audio can be improved by a circuit that biases the high audio frequencies. Hope to add the second 7 MHz oscillator on short notice.Dankjewel Pieter.

Tuesday, 11 November 2014

After inserting 2 new penlight AA-batteries in my 30 year old walkman, the device came to live. And the sound quality was not even bad. Amazing that music cassettes with this age still keep their magnetism !